1. Field of the Invention
The present invention relates to an optical characteristic measurement device and an optical characteristic measurement method, and particularly to a technique for measuring a spectrum with high accuracy.
2. Description of the Background Art
Conventionally, spectrometry has widely been used as a technique for evaluating an illuminant and the like. In an optical characteristic measurement device used in such spectrometry, a spectrometer (typically, a diffraction grating) is generally used to split light from an illuminant or the like, which is a measurement target, into a plurality of wavelength components and to detect each resultant wavelength component with a photodetector. In order to minimize influence of light other than light to be measured, the spectrometer and the photodetector are accommodated in a housing.
Actually, however, a result of detection by the photodetector may be affected by irregularly reflected light in the housing, light reflected in a diffused manner at a surface of the spectrometer, light having an order other than a measurement order, and the like. In general, such light is referred to as “stray light”. Various methods have been proposed in order to suppress influence of such unintended stray light.
For example, Japanese Patent Laying-Open No. 11-030552 discloses a method of correcting stray light by accurately estimating influence of the stray light generated in measurement of light guided from a dispersion optical system of a spectrophotometer with a light receiver having a large number of light-receiving elements as a measurement constant of the spectrophotometer and by eliminating that influence.
In addition, Japanese Patent Laying-Open No. 2002-005741 discloses a spectrum measurement device capable of obtaining an accurate spectrum intensity signal by eliminating influence of stray light generated within the spectrum measurement device or unnecessary light generated by reflection or diffraction at a surface of a detection element through processing of a detection signal.
According to the stray light correction method disclosed in Japanese Patent Laying-Open No. 11-030552, however, it is necessary to calculate a ratio between intensity of a light reception signal measured by each light-receiving element and intensity of a light reception signal measured by the light-receiving element corresponding to the split wavelength, as many times as the number of light-receiving elements constituting a detector. Therefore, this method is relatively time-consuming.
In addition, specific details of correction processing are not disclosed with regard to the spectrum measurement device described in Japanese Patent Laying-Open No. 2002-005741.